1. Field of the Invention
The present invention relates to a thin-film magnetic head comprising a recording head portion adapted to record magnetic information on a patterned media having minimum magnetization inversion units lined up with a nonmagnetic area sandwiched between them.
2. Explanation of the Prior Art
Recent recording media are required to have large capacities so as to cope with multidata such as pictures, images, and sounds.
To meet such demands, current HDDs (hard disk drives) have ever higher plane recording densities: the recording bit size of magnetic recording media is as fine as about 10 nm. To obtain outputs from such fine recording bits, each bit must make sure as large saturation magnetization and film thickness as possible. As the recording bit grows fine, however, it causes a decrease in the volume of magnetization minimum unit (V) per bit, which may otherwise offer a problem that magnetized information vanishes off due to the inversion of magnetization by “thermal fluctuation”.
Generally speaking, the smaller the value of Ku·V/kT (where Ku is an anisotropy constant, V is the volume of magnetization minimum unit, k is Voltzmann constant, and T is the absolute temperature), the larger the influence of that “thermal fluctuation” is, and experience has taught that as the value of Ku·V/kT is below 100, there is the inversion of magnetization occurring from the “thermal fluctuation”. In other words, the energy of magnetic anisotropy necessary for keeping the direction of magnetization of magnetic particles constant is represented by the product of the energy density Ku of magnetic anisotropy and the volume V of a magnetic particle: as this value grows small, there is the “thermal fluctuation” phenomenon taking place at room temperature, which may otherwise let recorded magnetization go off.
A magnetic recording medium of the longitudinal magnetic recording mode is highly susceptible of the “thermal fluctuation” even at the time when magnetic particles still keep large particle diameters, because the demagnetization field within recording bits at an area having high recording density grows strong. A magnetic recording medium of the perpendicular magnetic recording mode, on the other hand, is less susceptible of the “thermal fluctuation”, because if magnetic particles are allowed to grow in the thickness direction, the volume V of the magnetic field minimum unit can then be increased while the diameter of particles on the surface of the medium is kept small. With increasing recording density, however, resistance to thermal fluctuation will become insufficient even with the perpendicular magnetic recording mode.
As the media for solving such a thermal fluctuation resistance problem, attention is now directed to a magnetic recording medium called a patterned media. Generally, the patterned media is built up as a magnetic recording medium wherein multiple magnetic material areas each becoming a recording bit unit are independently formed in a nonmagnetic material layer. In a general patterned media, for instance, an oxide such as SiO2, Al2O3 and TiO2; a nitride such as Si3N4, AlN and TiN; a carbide such as TiC; and a boride such as BN is used as the material for the nonmagnetic layer, and the magnetic material areas each providing a recoding bit unit are selectively formed in the nonmagnetic material layer.
The patterned media, because of comprising a magnetic thin film divided to recording domain size, can have an increased volume V of the magnetization minimum unit, and get around the thermal fluctuation problem.
To achieve such a recording density as exceeding 1 Tbpsi, therefore, there must be the construction of the patterned media involved. And then, to achieve the recording density of 1 Tbpsi, the track width must be as narrow as possible. Still, the bit length must be as short as possible to increase the linear recording density, because the narrowness of the track width leads to a decrease in the recording magnetic field and a decrease in the fabrication yield. Typically, the track width and bit length should be about 50 to 70 nm and about 10 to 30 nm, respectively.
And now, for the purpose of making the thus set linear recording density of the patterned media effective and reliable and to make it much higher as well, of importance is upgrading the quality of recording (writing) bits, that is, the full inversion of magnetization of an associated bit (the inversion of the direction of magnetization of the bit): there is a demand for the proposal of the magnetic head best suited for recording on the patterned media. To put it another way, there is a demand for the development of a recording magnetic head that enables the direction of magnetization of physically isolated bits in the patterned media to be inverted efficiently, instantaneously, and reliably.
The situations being like this, the present invention has for its object the provision of a thin-film magnetic head comprising a recording head portion that enables the direction of magnetization of physically isolated bits in the patterned media to be inverted efficiently, instantaneously, and reliably.